diff --git a/src/method.rs b/src/method.rs
index 94e4d4ec..2d991f9c 100644
--- a/src/method.rs
+++ b/src/method.rs
@@ -377,7 +377,7 @@ mod extension {
         b'\0', b'\0', b'\0', b'\0', b'\0', b'\0', b'\0', b'\0', b'\0', b'\0', //   x
         b'\0', b'\0', b'\0', b'\0', b'\0', b'\0', b'\0', b'\0', b'\0', b'\0', //  1x
         b'\0', b'\0', b'\0', b'\0', b'\0', b'\0', b'\0', b'\0', b'\0', b'\0', //  2x
-        b'\0', b'\0', b'\0',  b'!', b'\0', b'\0', b'\0', b'\0', b'\0', b'\0', //  3x
+        b'\0', b'\0', b'\0',  b'!', b'\0',  b'#',  b'$',  b'%',  b'&', b'\'', //  3x
         b'\0', b'\0',  b'*',  b'+', b'\0',  b'-',  b'.', b'\0',  b'0',  b'1', //  4x
          b'2',  b'3',  b'4',  b'5',  b'6',  b'7',  b'8',  b'9', b'\0', b'\0', //  5x
         b'\0', b'\0', b'\0', b'\0', b'\0',  b'A',  b'B',  b'C',  b'D',  b'E', //  6x
@@ -466,4 +466,20 @@ mod test {
         let long_method = "This_is_a_very_long_method.It_is_valid_but_unlikely.";
         assert_eq!(Method::from_str(long_method).unwrap(), long_method);
     }
+
+    #[test]
+    fn test_extension_method_chars() {
+        const VALID_METHOD_CHARS: &str =
+            "!#$%&'*+-.^_`|~0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
+
+        for c in VALID_METHOD_CHARS.chars() {
+            let c = c.to_string();
+
+            assert_eq!(
+                Method::from_str(&c).unwrap(),
+                c.as_str(),
+                "testing {c} is a valid method character"
+            );
+        }
+    }
 }